3.4 Analysis And Synthesis

Question 1

What is another name for a positive ion?

Answer 1

A cation

Question 3

What is the method for a flame test?

Answer 3

Nichrome wire is cleaned by repeatedly placed in hydrochloric acid
Dip the wire in more hydrochloric acid and into the compound to be tested
Place in the Bunsen flame and see what colour is produced from the compound

Question 4

What are the tests for positive ions?

Answer 4

Flame test

Reaction with sodium hydroxide

Question 5

What is the flame test for lithium?

Answer 5

Crimson (red)

Question 6

What is the flame test for sodium?

Answer 6

Yellow

Question 7

What is the flame test for potassium?

Answer 7

Lilac

Question 8

What is the flame test for calcium?

Answer 8

Red

Question 9

What is the flame test for Barium?

Answer 9

Green (pale)

Question 10

What is the flame test for copper?

Answer 10

Green

Question 11

What is the precipitate colour when you react sodium hydroxide and Aluminium?

Answer 11

White

Question 12

What is the precipitate colour when you react sodium hydroxide and calcium?

Answer 12

White

Question 13

What is the precipitate colour when you react sodium hydroxide and magnesium?

Answer 13

White

Question 14

What is the precipitate colour when you react sodium hydroxide and copper?

Answer 14

Blue

Question 15

What is the precipitate colour when you react sodium hydroxide and iron II?

Answer 15

Green

Question 16

What is the precipitate colour when you react sodium hydroxide and iron III?

Answer 16

Brown

Question 17

What is another name for a negative ion?

Answer 17

Anion

Question 18

What ions are tested for in tests for negative ions?

Answer 18

Carbonate
Sulfate
Chloride
Bromide
Iodide

Question 19

What is the test and the result for carbonate ions?

Answer 19

Add hydrochloric acid

It fizzes giving off CO2 (use limewater to check)

Question 20

What is the test and the result for sulfate ions?

Answer 20

Add hydrochloric acid then barium chloride solution

A white precipitate is formed

Question 21

What is the test and the result for chloride, bromide and iodide?

Answer 21

Add nitric acid then silver nitrate

Chloride - White precipitate
Bromide - Cream precipitate
Iodide - Yellow precipitate

Question 22

What does Aluminium do?

Answer 22

The only precipitate that dissolves in excess sodium hydroxide solution

Question 23

What is titration used for?

Answer 23

A neutralisation reaction
Acid + alkali -> salt + water

The volumes of the solutions that react exactly can be found

Question 24

What is the method for titration?

Answer 24

Fill the burette with acid to the zero mark
Measure the alkali using a pipette then put into a conical flask
Add 3-4 drops of universal indicator to the alkali (pink colour)
Add the acid a few drops at a time until the solution is almost colourless
Drop-wise add 1 at a time until solution is completely colourless
Record the volume of acid needed for neutralisation (end point reached)
Repeat and take average result

Question 25

In titration calculations what is the equation?

Answer 25

Moles = concentration x volume

Moles: mol
Concentration: mol/dm3
Volume: dm3

Question 26

How do you convert to decimetres?

Answer 26

Cm3 divided by 1000

Question 27

At neutralisation...

Answer 27

Moles of acids are equal to moles of alkali

Question 28

In chemical analysis what is a qualitative method?

Answer 28

Finds out if a substance is in a sample

Question 29

In chemical analysis what is a quantitive method?

Answer 29

Finds out how much of a substance is in a sample

Question 30

What are the advantages of instrumental methods?

Answer 30

Quick Accurate Only a small sample size needed

Question 31

What are the disadvantages of instrumental methods?

Answer 31

High equipment cost Needs frequent calibration Specialist knowledge needed to operate

Question 32

What are just qualitative methods?

Answer 32

Mass spectrometry- provides RFM Atomic absorption spectrometry - absorbs light to reveal the energies needed to excite an electron to another energy level

Question 33

What are qualitative and quantitive methods?

Answer 33

Gas chromatography - separates a mixture of components into individual components Infra-red spectrometry - identifies particular covalent bonds in a molecule